Engine stop-and-start systems, such as idle reduction control systems, have been recently developed. Such engine stop-and-start systems are designed to automatically stop an internal combustion engine of a vehicle in response to detecting a driver's engine stop operation, such as the operation of a brake pedal. These engine stop-and-start systems are also designed to restart the internal combustion engine in response to detecting a driver's operation to start the vehicle, such as the operation of an accelerator pedal. These engine stop-and-start systems aim at reducing fuel cost, exhaust emission, and the like.
Restarting an internal combustion engine, referred to simply as an “engine”, requires initial rotation of an output shaft, such as a crankshaft, of the engine as well as normally starting the engine in response to the operation of an ignition key. These engine stop-and-start systems use a starter to provide initial rotation to the crankshaft of the engine. Specifically, in order to provide initial rotation to the crankshaft of the engine, these engine stop-and-start systems shift a pinion of the starter to a ring gear coupled to the crankshaft to thereby engage the pinion with the ring gear. Thereafter, these systems energize the starter to rotate the pinion to together with the ring gear to start cranking of the engine, thus restarting the engine.
An example of starter drive control for restarting an engine is disclosed in U.S. Pat. No. 7,275,509 corresponding to Germany Patent Application Publication No. DE 10 2005 049 092 and to Japanese Patent Application Publication No. 2007-107527. The starter drive control disclosed in these patent Publications pre-engages the pinion of the starter with the ring gear coupled to the crankshaft of the engine during the crankshaft coasting (being rotated without the aid of the engine) after automatic stop of the engine in preparation for restart of the engine. This pre-engagement of the pinion with the ring gear can restart the engine immediately in response to the driver's engine restart operation, and can reduce noise to be generated when the pinion is engaged with the ring gear.